Anti-Inflammatory Property of 5-Demethylnobiletin (5-Hydroxy-6, 7, 8, 3′, 4′-pentamethoxyflavone) and Its Metabolites in Lipopolysaccharide (LPS)-Induced RAW 264.7 Cells

SIMPLE SUMMARY: 5-Demethylnobiletin (5-hydroxy-6, 7, 8, 3′, 4′-pentamethoxyflavone, 5DN) is a bioactive polymethoxyflavone mainly found in citrus plants. To our knowledge, the present study is the first report on the inhibitory mechanism of 5DN and its metabolites on LPS-induced inflammation in RAW 264.7 macrophage cells. Importantly, 5DN’s metabolites showed more potent activities than the parent compound. The possible relationship between the structural properties of 5DN and its metabolites and their anti-inflammatory activity deserves further investigation. ABSTRACT: Hydroxylated polymethoxyflavones (PMFs) are a unique class of flavonoid compounds mainly found in citrus plants. We investigated the anti-inflammatory effects of one major 5-hydroxy PMF, namely 5-demethylnobiletin (5DN) and its metabolites 5, 3′-didemethylnobiletin (M1), 5, 4′-didemethylnobiletin (M2), and 5, 3′, 4′-tridemethylnobiletin (M3) in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. The results showed that M2 and M3 produced stronger inhibitory effects on the production of nitric oxide (NO) than their parent compound at non-cytotoxic concentrations. Western blotting and real-time PCR analyses demonstrated that M2 and M3 significantly decreased iNOS and COX-2 gene expression. The results also showed that M1 and M3 induced heme oxygenase-1(HO-1) gene expression. Overall, our results demonstrated that metabolites of 5DN significantly inhibited LPS-induced inflammation in RAW 264.7 macrophage cells and generally possessed more potent anti-inflammatory activity than the parent compound, 5DN.